Field of the Invention
The present invention relates to a wound stator of an alternator, more particularly to a wound stator of an alternator having double abreast wires embedded in grooves of a stator.
Description of Related Art
An alternator is used for converting mechanical energy into alternating-current electric energy. In a vehicle alternator, the output power of an engine drives a rotor of the generator to rotate within a stator to convert mechanical energy of the engine into electric energy to charge a storage battery, which then supplies electric energy to electrical parts of a vehicle.
A vehicle alternator typically has an annular stator and a rotor. By means of rapid rotation of the rotor in the stator, magnetic fields are formed by wires wound on the stator so as to generate an induced electromotive force (voltage) in the wires. In general, the voltage output by the alternator is proportional to the number of coil groups in a stator ring. Therefore, the higher the density of wires wound on a stator ring, the higher the power generation of the generator.
A variety of coil winding methods have been adopted for a conventional generator, such as folding and winding, or wave-shaped winding. The choice of winding method has an influence on the output voltage of the generator at low rotational speed or high rotational speed resulting in specific output characteristics of an alternator at different rotational speeds. For example, factors concerning the output characteristics of an alternator include the diameter of the conducting wires and the number of wound coils. Under high rotational speed, the output current of the alternator usually increases or decreases along with the wire diameter. Furthermore, under low rotational speed, the output current of the alternator usually increases or decreases along with the number of coils. Therefore, design choices of conducting wire diameter and winding method vary depending upon the desired output characteristics.
Moreover, the stator of an alternator is positioned such that it surrounds the rotor. When the rotor is rotated with respect to the stator, the coils wound on the stator are induced because of electromagnet effect and thus generate alternating current. The rotor normally comprises a first claw pole element and a second claw pole element in which a plurality of the N-pole claw-shaped bodies of the first claw pole element and a plurality of the S-pole claw-shaped bodies of the second claw pole element are respectively adjacent to each other while spaced apart. After an electric current is supplied to the magnetic-field coil of the rotor 1, a claw pole element of the poles and the other claw pole element can be magnetized into an N pole and an S pole, respectively, due to electromagnetic induction so that each pair of adjacent claw-shaped bodies of the claw pole elements can generate a magnetic field. When the rotor rotates, direction of the magnetic field also changes with rotation of the rotor to further create an electromagnetic induction with the stator coils of the stator to generate an alternating current. However, for a rotor of a generally conventional alternator, after an electric current is supplied to the magnetic-field coil and when the first claw pole element and the second claw pole element of the pole are magnetized into an N pole and an S pole, respectively, due to electromagnetic induction, part of the magnetic lines may directly pass from a space between two adjacent claw-shaped bodies of the claw pole elements and may not participate in formation of the magnetic field of the pole. Such phenomenon is called “magnetic leakage.” Magnetic leakage may cause unnecessary magnetic loss and reduce the strength of the magnetic field formed by the pole, which further reduces the generating capacity of the alternator.
In view of the above, optimization of a wire structure and the winding manner as adopted for the wound stator, and also improvement to the rotor structure are desired in order to enhance the output efficacy of an alternator.